slip the female dovetail over the male dovetail on the optic mounting rail untill the fore-to-aft stop contacts the rail. throw the locking lever 180° to lock the scope on the rail.

if the locking lever needs adjusted to provide increased or decreased grip pressure on the rail, see your scope's instruction for doing so (it is simply a matter of holding the locking lever stationary while tightening or loosening a nut that is threaded onto the locking lever's shaft.